Fuse cutout construction



May 27, 1958 E .SANKEY FUSE CUTOUT CONSTRUCTIO Filed June 22, 1955 [al l INVENTOR. BY ward L. San/(gr 3 ,0 //////////////4l .v//l

ATTORNEY FUSE CUTUT CONSTRUCTION Edward L. Sankey, Milwaukee, Wis., assgnor to McGraw- Edison Company, a corporation of Delaware Application .lune 22, 1955, Serial No. 517,248

6 Claims. (Cl. 200-114) The present invention relates to a fuse cutout construction, and particularly relates to a cutout characterized by its ability to safely close an electric circuit even though fault conditions may exist thereon.

When a high voltage protective fuse link ruptures, it is the present practice to restore circuit continuity by removing the fuse cartridge from its holder, substituting a new fuse link therein and replacing the cartridge in the cutout assembly, thereby reclosing the electric circuit.

Occasionally, however, the fault which caused the excessive ilow of current that ruptured the original fuse link still remains on the line when the lineman is attempting to reclose the circuit with a re-fused cartridge. Under these conditions, where prior art fuses were used, violent arcing often occurred at the moment when the upper movable terminal of the fuse cartridge contacts its cooperating stationary terminal. This arcing is frequently accompanied by melting of the metal contact parts, and by a profused evolution of hot gases. i

In the case of housed cutouts, these devices are constructed with suiiicient strength to counteract any expulsive forces caused by rupture of the fuse link when all of the parts are in secure mechanical engagement relative to one another, This is true even in the relatively confined space provided in the cutout housing. However, when an attempt is made to reclose the cutout on the existence of a low impedance fault without secure mechanical engagement, the confined hot gases act immediately to force the cutout door open with such violence as to injure or burn the lineman vwho is servicing the fuse. In some cases, there is even the possibility of the porcelain housing being blown apart by the evolution of relatively conned gases.

It is an object of this invention to overcome the above noted defects by providing a fuse cutout construction which may be safely restored to closed circuit position even on the existence of a low impedance fault in the system to be protected by the fuse.

Another object of the present invention is to provide an interchangeable cutout construction which may be conveniently inserted in present standard cutout assemblies without requiring any modication of the stationary cutout members, and, in fact, without requiring more than very minor modications of the cartridgedoor assembly itself.

A further object of the present invention is to provide a cartridge-door assembly for enclosed cutout constructions which may be conveniently inserted in standard cutout boxes for testing the circuit to determine if a fault exists in the system prior to insertion of the original refused cartridge-door assembly.

Still another object is to provide a cutout which permits secure mechanical closing prior to re-establishing circuit continuity after rupture of a fusible element, and which cutout enables a lineman to close the circuit thereafter from a safe remote position through the agency of an insulated stick.

Other objects will appear from time to time throughout the following specification.

nited States Patent O An embodiment of the invention is shown in the accompanying drawing, in which:

Fig. 1 is a side elevational view, in section, showing an embodiment of the fuse cutout in conjunction with an insulating cutout box, the fuse cartridge assembly being shown in non-conductive position;

Fig. 2 is a fragmentary sectional View of the fuse illustrated in Fig. 1, after it lhas been tripped to conductive position.

Referring to Fig. 1 of the drawing, it will be seen that the fuse cutout comprises an insulating housing 1 which is supported on a metallic bracket 2 and a door 3, also of insulating material, hingedly supported on the housing by means of trunnions 4 which extend laterally from the lower edge of the door and are removably seated within the spaced apart hook-like portions of a rigid bracket 5 atiixed to the housing. The door 3 is adapted to pivot into closed relation with housing 1 and to be removed from the bracket S. The construction of the hinge assembly is well-known, and has been illustrated here in dotted portions for convenience and minimum of confusion in disclosing the novel features of the present structure.

Referring to Fig. l, it will be seen that the insulating door 3 txedly carries on it a fuse cartridge assembly, indicated generally by the reference numeral 10. When the door 3 is closed with respect to housing 1, as illustrated in Fig. l, the upper terminal cap 11 of cartridge 10 con.- tacts and becomes electrically engaged with an upper stationary terminal 12 affixed within the housing in electrical association with a pair of Ushaped yieldable clips 13 which serve to guide the cap 11 into alignment with the terminal 12. Members 12 and 13 are connected to an incoming electric line conductor by means of a screw type connector 14.

Disregarding for a moment the conductive assembly within fuse cartridge 10, attention is directed to the lower portion of housing 1 where it may be seen that the outgoing line conductor from housing 1 is connected through the medium of connector 20 to a lower terminal in the form of a U-shaped member 21, and is anchored thereon by means of a screw 19.

When the door 3 is swung to closed position, as shown in Fig. l, the lower stationary terminal clips 21 are adapted to electrically receive therebetween a conductive contact 22 which in turn supports the cartridge assembly 10. The lower fuse tube contact 22 is rigidly atlixed to the door by means of screws 23 to prevent the cartridge assembly 1t) from sliding with respect to the lower contact 22. To further secure the cartridge from sliding axially relative to the contact 22, a straight pin 24 is driven through the contact and engages the outer peripheral wall of the fuse tube 27.

Fuse tube 27 is also embraced adjacent its lower end by a forked plate 2S which is attached by means of screws 2% to a rigid conductive appendage 30 extending from and cast integrally with the lower fuse tube contact 22. It is preferable to insert a soft rubber sleeve 31 between the forked plate 28 andfuse tube 27 to provide a gas barrier to prevent ilashover between the spaced-apart terminals during normal interruption of the fuse link.

As will be evi-dent from the drawing, the lower extremity of appendage 3? pivotally supports a fuse link throwout lever 35 by means of a pivot pin 36 surrounded by a coil spring 37, which acts to bias throw out lever 35 in a clockwise direction. A exible conductive leader 34 extending from the lower end of fuse tube 27 is pulled tightly over the throw out lever 35 so as to restrain it against the lower end of `fuse tube 27. The free end of leader 3d is brought back and around a threaded stud 33 staked to the appendage 3) and to which the leader is electrically connected by means of a knurled thumb screw 39. Thus, it is seen that there may be electrical continuity through cartridge assembly 10 to outgoing line terminal 20 through an intermediate path comprising leader 34, appendage 30, lower contact 22, and lower U-shaped terminal 21. Y

Attention is now directed to the improved fuse cartridge assembly 10 and its associated cooperating elements, wherein the principal features of novelty reside. Cartridge assembly 10 may 'be dimensionally adapted to be mounted on any standard insulating fuse cutout door 3. Essentially, the cartridge comprises a tube Z7 of any hard insulating material, such as that sold under the trademark Bakelite, threaded at one end 44 for receiving a conductive fuse terminal cap 11. Cap 11 electrically en gages the yieldable stationary contact clips 13 anchored in housing 1 when the door 3 is closed. Interiorly, tube 27 is provided with a snug ttinghorn ber liner 4S, whic is capable of evolving copious quantities of non-ionized gases when subjected to higt temperatures associated with an electric arc. Above the mid-point within the tube 27, the fiber liner 45 terminates in a radially inwardly extending shoulder 46 which normally supports a button like c-ontact 47. In this embodiment, the 'button contact 47 forms one terminal of a fuse assembly including a fusible element 48 to which is attached a flexible leader 34, referred to hereinbefore, and preferably made of braided `copper wire.

It will be observed that button 47 is restrained tightly against shoulder 46 by means of an insulating tube 49 slidable relative to the tube 27, and which extends outwardly beyond the upper end of tube 27 and the cap 11 so that it is compressed when the cap 11 is turned tightly onto the tube. By tightly holding down button 47 in this manner, the hot gases which accompany rupture of fusible element 48 are prohibited from escaping upwardly above the button; however, the hot gases and fuse exible leader 34 may be ejected from the lower end of fuse 27. The complete removal of the leader after rupture is assisted by the action of spring biased throw out lever 35.

In Fig. l, the cartridge assembly is in cocked position after insertion in the porcelain housing. lt is to lbe noted that all of the cooperating parts are in secure mechanical engagement. Electrical discontinuity is accomplished by providing the bore of the insulating tube 49 with a slidable copper tungsten 4alloy butt type contact, hereinafter called tip 51, restrained in spaced relation with button contact 47 so as to provide an air gap 41 between them when the fuse cartridge 10 is initially inserted between upper terminal 12 and lower fixed terminal 21. It will be noted that tip 51 is' electrically connected to cap 11 through the medium of a disc 52 disposed between cap 11 and tube 49, and which is in turn yconnected to tip S1 through a llexible braided leader 53. As is evident from the drawing, disc 52 is preferably perforated at the center `and depressed thereabout to receive an end yof leader 53. The central depression in disc 52 facilitates soldering the leader to the disc at 54.

In Fig. 1, the tip 51 is biased toward button 47 by the action of a relatively strong compression spring 56. Tip 51 is maintained in this cocked position in opposition to spring t) by means of an S-shaped detent pin 56 extending through an -aperture 7 in tubes 27 and 49 into the path of movement of tip 51. Detent 56 is adapted for advancement and retraction with respect to tip 51 by means of a trip lever 5S which is in turn adapted to rock on a pin 59 carried by post 60 rmly anchored in the body of door 3 by any suitable means. Trip lever 58 is preferably connected to detent 56 by means of a laterally extending pin 61 slidably positioned in a transverse aperture 62 in the trip lever to prevent binding between cooperating members.

As stated earlier, it is intended that the improved cartiidge assembly be used either as a permanently installed component of a fuse cutout, or in the alternative, jas a temporary safety device for testing an electrical linesub-V sequent to replacement of a blown fuse link assembly.

In illustrating the operation of the invention, it will be assumed that cartridge assembly 1d and door 3 are mechanically secured in operating position cooperating with the element within housing 1. lf it is desired to replace a ruptured fusible element 43, door 3 and likewise cartridge assembly are swung outwardly on trunnions 4 and removed from the hook-like bracket 5. After removal of the assembly from housing 1, cap 11 is unscrewed and the unitary structure consisting of disc 52, spring 50 and tip 51 is removed from the tube 49. Then, by means of pivoting trip lever 58, detent pin 56 is retracted to allow removal of insulating tube 49. This releases the button 47 for removal from the cartridge assembly 10 by merely inverting the latter.

After a new fuse link 48 has been substituted, liber tube 49 is then inserted within the outer Bakelite tube 27 and trip lever 53 is rocked to advance detent 56 radially inwardly of tube 49. Butt contact tip 51 is then placed in the tube abutting detent 56, and finally cap 411 is screwed into place so that it fully compresses coil spring Si). The door 3 and cartridge 1G assembly is now ready for replacement in housing 1 in cocked or open circuit position, see Fig. l.

Since tip 51 is restrained in circuit open position away from button 47, door 3 may be fully mechanically closed without completing the electric circuit through the cutout'. Consequently, even though a fault remains on the electric circuit, no arcing or flashing will occur nor will any danger ensue to the lineman closing the fuse box because the cartridge 10 is non-conductive up to this time, However, when the door is closed, positive electrical connection may be made immediately thereafter between the U-shaped upper yieldable clip 13 and fuse terminal cap 11.

After the lineman removes himself from the immediate vicinity of the fuse cutout, he may engage trip lever 58 by means of an insulated stick and rock the trip lever so that detent 56 is retracted from the path of tip 51. This step, of course, permits tip 51 to make abrupt contact with button 47 under the influence of'compression spring 50. Hence, as is evident from Fig. 2, the electric circuit, from cap 11 through the fuse assembly and flexible leader 34 will becompleted.

confined to the interior Should a fault remain on the line after the fuse assembly is closed in, and after trip lever 58 is actuated, fusible element 4S may rupture duc to the over-current, but no serious consequences will result because all arcing will be of cartridge 10 which is designed for that duty. Hence, it is to be appreciated that the invention completely eliminates premature arcing between the terminals of the cutout construction which arcing would occur when merely closing a faulted system when conventional cutouts are employed. Moreover, it is obvious that a lineman can close the novel cutout without skepticism as to whether Violent flashing may occur before the cutout door is fully closed.

, As implied hereinbefore, it is not necessary to secure the benefit of this invention that every cutout in the electric system be provided with the novel fault make fuse cartridge herein described. Rather, the invention is adapted to be used in a cutout having any proper correspending current rating. Thus, if need be, a line crew truck may carry only one such device for each conventionally rated cutout in a system, andwhencver it is desired to refuse a cutout where a reasonable doubt exists as to whether or not the fault has been cleared, the present cartridge-door assembly may be temporarily installed and actuated to determine whether or not the fusible element therein will rupture. lf it does not, of course, door 3 carrying the cartridge asernbly 10 may be removed and the standard cutout door assembly substituted therefor. The circuit may then be safely and confidently disclosed.

In summary, it will be noted that the invention features a novel safety fuse cutout assembly which may be operated to closed circuit position without danger to the lineman, and wherein premature uncontrolled arcing is precluded. Moreover, it will be noted that the construction is such as to include a minimum amount of moving parts and is rugged, highly simplified and economical. Although the disclosure will suggest to those versed in the art many modifications of the novel device described herein, and although only a preferred embodiment is illustrated, it is intended that the scope of the invention be limited only by the purport of the claims which follow.

I claim:

1. In combination with a circuit maker having spaced terminals, a fuse cartridge assembly electrically bridging said terminals, said fuse cartridge having interiorly thereof a fusible element and a Xed and a movable contact normally maintained in spaced relation, spring means biasing said contacts toward each other, latch means normally restraining said movable contact in spaced relation with said iixed contact in opposition to the action of said spring means before said spaced terminals are mechanically bridged, manually operable means for rendering said latch means ineffective to restrain said movable contact, whereby said movable contact may be released to contact relation with said fixed contact by operating said manual means after the terminals are positively mechanically bridged by said fuse cartridge.

2. In a circuit maker having spaced terminals, a fuse cartridge assembly disposable in electric bridging position across said terminals, said fuse cartridge including an insulating tube having an end terminal engageable with one of said spaced terminals, a stationary contact disposed Within said tube, a movable contact normally spaced in a rst position from said stationary contact, spring means interposed between said end terminal and said movable contact biasing said movable contact toward said stationary contact, detent means restraining said movable contact in opposition to said spring means, a fusible element in conductive relation with said stationary contact and having a portion projecting from said insulating tube, and manually operable trip kmeans operatively connected with said detent means whereby said movable contact may be released for electric engagement with said stationary contact.

3. In a circuit maker having spaced terminals, a fuse cartridge assembly disposable in bridging position across said terminals, said fuse cartridge comprising an insulating tube having a conductive end terminal engageable with one of the spaced terminals, said tube having a path therethrough including a stationary contact and a movable contact separated by a gap, spring means urging said movable contact toward said stationary contact, detent means restraining said movable Contact in opposition to said spring means, a fusible element electrically connected with said stationary contact and having a portion projecting from said tube, manually operable means for actuating said detent means to release said movable contact and thereby close the gap between said stationary and movable contacts.

4. In a circuit maker having spaced terminals, a fuse cartridge assembly disposable in bridging position across said terminals, said fuse cartridge comprising an insulating tube having an end terminal engageable with one 6 of said spaced terminals, a fusible element including a stationary contact within said tube and a flexible portion extending therefrom, a movable contact in a first position spaced from said stationary Contact and movable to a second position contiguous with said stationary contact, spring means interposed between said end terminal and movable contact urging the latter toward the former, detent means projecting through said insulating tube into the path of said movable Contact, manually operable means for retracting said detent means from the path of said movable contact thereby permitting said movable contact to move to said second position and complete an electric circuit through said fuse cartridge.

5. In combination, a circuit maker comprising an insulating housing having spaced terminals therein, an insulating door for closing said housing, a fuse cartridge assembly mounted on said door for bridging said spaced terminals when said door is closed, said fuse cartridge assembly comprising an insulating tube having a fusible element therein with a portion extending from said tube and a stationary contact electrically connected to said element, a movable contact spaced from and movable toward said stationary contact within said tube, spring means urging said movable contact toward said stationary contact, detent means engaged with said movable contact and projecting through said door, manually operable means exteriorly of said door acting through the medium of said detent to release said movable contact into contiguity with said stationary contact after said door is fully closed.

6. In combination, a circuit maker comprising an insulating housing having spaced terminals therein, an insulating door for closing said housing, a fuse cartridge assembly rigidly carried by said door for bridging said spaced terminals when said door is closed, said cartridge including an insulating tube having a concentric liner defining an arcing chamber, a fusible element having a portion projecting from said tube and a stationary contact portion supported on said liner, a conductive cap on said tube, an insulating sleeve compressivery held against said stationary contact by said cap, a movable contact electrically connected to said cap and slidable toward said stationary contact, spring means urging said movable contact toward said stationary contact, detent means projecting through said sleeve and said tube into the path of said movable contact in opposition to said spring, said detent means projecting also in the opposite direction freely through said door, a manual trip lever exteriorly of said door for releasing said movable contact through the medium of said detent means into contiguity with the stationary contact after the door is fully closed.

References Cited in the tile of this patent UNITED STATES PATENTS 2,087,744 Triplett July 20, 1937 2,299,196 Wallace Oct. 20, 1942 2,472,625 Smith June 7, 1949 2,617,908 Lincks Nov. l1, 1952 2,663,825 Amundson Dec. 22, 1953 2,677,738 Schneider May 4, 1954 

